Method and apparatus for noise control of reproduced sound



Dec. 28, 1948. o soN ETAL 2,457,712

- METHOD AND APPARATUS FOR NOISE CONTROL OF REPRODUCED SOUND Filed Sept. 21,- 1945 2 Sheets-Sheet 1 mm. m. x n a, hm. v. TJ. N y \N. B I l.- 1 .1 My A N? N NM w\ A \N A Nx \w m N L\ .5 A v A AR 2% m .w\. v mi OIRQOOQ T v wwtbu Y Q.

ATTORNEY Dec. 28, 1948. OLSON E 2,457,7i2

METHOD AND APPARATUS FOR NOISE CONTROL OF REPRODUCED sown Filed Sept. 21, 1945 2 Sh eets-Sheet 2 g laosscr l 77M! sou/v0 544-2 215' INVENTORS Meey 1? 0.450 I 8 JOHN PA sro/v 'BY @QM A TORNEY Patented Dec. 28, 1948 METHOD AND APPARATUS FOR NOISE CONTROL OF REPRODUCED SOUND Harry F. Olson, Princeton, and John Preston, Hopewell,- N. J., assignors to Radio Corporation of America, a corporation of Delaware Application September 21, 1945, Serial No. 617,858

The present invention rel-ates to phonographs and particularly to the control of sound output relative to ambient noise.

In the operation of phon'ographs, so called juke boxes and the like, and particularly in ublic places, the ambient noises are a highly disturbing factor to persons desirous of obtaining the benefit of the sound output of the phonograph. Thus, in one instance, the ambient noise may be of such a magnitude as to either drown out the sound entirely, or be so disconcerting that the output cannot be appreciated, and in another instance, the ambient noise may be of such minimum volume that the sound output becomes unbearably loud with the result the reproduction of the music or other reproduced sound loses that quality so necessary to the cultivated musical ear. For example, in public places the noise level increases as the number of people increase, so if the level is correct for an empty restaurant, then the music cannot be heard when the restaurant is filled.

Some of the objects of the present invention are: to provide a novel system of music to noise control; to provide means for maintaining automatically a predetermined difference in level between the sound output and the ambient noise in a sound reproducing system; to provide a control system for phonographs, magnetic wire recording and reproducing systems and thelike wherein the output is automatically regulated as a function of the ambient noise; to provide a method of maintaining a predetermined difference in noise level between reproduced sound and ambient noise; to provide a means for and a method of regulating the sound output of a phonograph of the record-changer type during the intervals between the playingoi the sound records whereby the next record will be'played automatically at the selected level; and to provide other improvements as will hereinafter appear.

In the accompanying drawings, Fig, 1 represents diagrammatically a sound output-noise system embodying one form of the present invention; Fig. 2 is a sound level time graph; and Fig. 3 is a volume control displacement time graph.

Referring to the drawings, one form of the present invention consists of a volume control unit ll! of the type ordinarily employed in a phonograph for controlling the amplified sound as delivered from the pick-up II which rides in the sound trackof preparedrecords. It is the purpose of the present invention to control automatically the output of the unit Ill as a function 4 Claims. (Cl. 179-1) t of the ambient noise in the room where the phonograph is located.

In order to control the volume unit l9 so that the difference in level between the phonograph sound output and the ambient noise is constant, the circuit of the volume unit It includes a potentiometerl2 having a control pointer l3 fixed to a split shaft [4 which is arranged to be turned and set by a novel proportioning system functioning in response to ambient noise received by a microphone l5 and amplified by an amplifier IE. The output of the amplifier I6 is set to a selected sound level by an auxiliary volume control ll having its output in a circuit including a motor l8 of the type wherein the motor speed is proportional to the voltage input. A-rectifier 9 is provided when a D.-C. motor is used. If an A.-C. motor is used the rectifier is not required. During this sampling of the ambient noise the phonograph pick-up l I is automatically rendered inoperative but is restored to operation at the conclusion of the sampling step. The shaft I4 is arranged to be driven by the motor l8 through the medium of reduction gearing 20. A clutch 2 I, the latter having one toothed member 22 keyed to one of the meeting ends of the shaft l4 and having the other toothed member ,23 keyed for sliding movement on the other of the meeting ends of the shaft M. This latter member 23 includes a portion which is circumferentially slotted to receive the forked end of the clutch actuating lever 24, which is suitably pivoted to a fixed part. This lever 24 is arranged to engage and disengage the clutch 2| by a solenoid 25 and spring 26.

For returning the potentiometer pointer l3 to zero for setting to a new volume control, a torsion spring 21 is attached at one end'to the shaft [4 and at the other end to a fixed point so that in unclutched condition the spring 21 biases the pointer Hi to its zero position.

From the foregoing it will be seen that the cycle of operation includes a means for rendering the pick-up inoperative, a means for setting the.

volume control to zero, a means for sampling the ambient noise and setting the volume control proportioned to such ambient noise, and means for restoring the pick-up to operation and thereby reproducing the sound at the required level in accordance with the set position of the volume control. The foregoing means are all automatically controlled by the operation of a cam 30 of a record changer as set forth in United States patent to Thompson, No. 2,012,326, reference to which may be had to supplement the present description.

34 and a contactor switch 35, thisqatter-having,"

its contactor extending into the path of "a projec tion 36 carried by the cam 30 and the operation: is such that when the projectionWB- sna the contactor, the switch 35 momentarilrclosesthe solenoid circuit so thatizthesclutch:.lever:24: disconnects the clutch 2| whereupon the. torsion spring 21 returns the volume control polntnto Immediately thereafter the solenoid is dezero. energized and'i'the spring-*26 shifts' tlie levenM to reengage the clutch 2| ready to' reset'ithe=pointer for the"nextsampling noise-level.

For controlling the' 'switchihg in and out of the-- ambient-noise sampling-"Unit? a (:Orlta ctorswitch 31 is'-' included in the sampling circuit I for 7 themotor [8 'and--has its' conta'ctor arrangedin thepath of 'the cam-' 3|]; the timingposition being-- such as to close the noise sampling circuit" just after the volume control ID has been 'setto-'zero"- and 'whil the pick-up circuit is" short 'cir'c'uited:

Thus; the-noise samplingfcircuit and -the pick-- up circuit are alternatelyoperated in su'c'h a manner" that after each record 'isplayed the ambient .noi's'efis sampled "and th e' volume control set accordingly; The operati'on'and stepsmf the method are as" follows: Assuming a record has just" finished playing; thecam" 3fl"oi the" record changer will cause the projection 35 to actuate through the. gearing'ZII" and clutch 2! to the potentiometer pointer l3','".which,is moved to the required position as determined! byth'e ambient noise level. After this. setting. of? the; volume. control, the cam 30fm'ove's beyond" the-switch contactor so that theiswitc'hes are automatically returned to again bring. the pick u'p. ll. into operation and "to; render. the l sampling circuitin.- effectiv'e." This'cycl'eiis repeated'aft'er each.1'ec= ord;so thatthere is alternate sampling offambient' noise 'and'playing of the. records;

Whilein the foregoing a 'separateamplifieii is provided" for the sampling microphone,1the"in vention'. contemplates. having. a common amplifier fori'the microphone and for the phonograph; in" wl'iichl case. addit'onal switching means 1 are. to. i-be1 provided'j whereby. at.the.'proper time the Icycle. the" common. inp'utl amplifier can? be. alternately j conn'ected'lto the output of. the microphone. and .1 the ou't'putoffthe phonographpickup. Thus, at' the time. the motor l '8"i's to operate, the amplifier output circuit'would'be "switchedffrom'the phonographoutputito the'mi'crophonej output.

We? claim;as-ioufiinvention:

1. Apparatus for regulating the difference in level between reproduced sound and ambient noise, comprising the combination of a phonograph volume control, an electrical circuit including a pick-up for reproducing sound from a record, a microphone responsive to ambient noise, means' for translating ambient -noisereceived by said' mirophone into electrical energy, means operated by said energy for setting said volume control proportionately to the ambient noise, and

selective switchingmeans automatically operable for alternately; connecting said setting means and'said pick u'p'to said volume control.

; Z.'*App aratu'si for regulating the difierence in {lever between reproduced sound and ambient noise? comprising the combination of a phonographrvolume: control, an electrical circuit including a pick-up for reproducing sound from a recorrand also including said volume control, a microphone responsive to ambient noise, means fortrans1atin zi ambient .noise received; by said microphone into electrical. energy,,meansoper ated by said energy for setting *saidi'volumecon trol proportionately to :the ambient :noise, a rec- 0rd changer; and smeans operat-ed: by saidrecord changer for alternately: connecting said settingniaiis and fsaid 'pi'ck upz to said volume control;

Si -Apparatus for. regulating the difference in level" between reproduced? sound'. and ambient noiseycomprisinga the combination' of a phone:- gfa'ph'i-I vol-um'e' control; an electricalcircuit in eluding a pick- 11p for" reproducing sound from a record,- said 1; circuit also including said. volume? control? meansincluding: a" microphone and an; arilplifir iontranslating ambient noiseiinto elecgtrical energy; means'ior settingsaid volume conetrol to zero: output, means operated by: said energyfor setting said 'voliime' control' proporetionately to th'eambient noise;.means forxrendering said pick -up'inoperative during the opera.- tion* oi' said setting means; and means; torrenderr said pick-up operative after the volume setting. meanszhas functionedi.

4;" Apparatus for regulating the-- difference: in level? betweeni reproducedsound. and ambient noise; comprising" the: combination of: a phonograph? volume control; an. electrical circuit including a Fpickeuprforrreproducing sound from a record,". said;- circuit also: including. said volume control ,2 means including; a. microphone and an amplifier: for translating; ambient-noise ,into electrical energy; means for; setting said: volume controlf'to. zero=output-,- means operated by said-en erg-y; for setting said vo1ume:- control proportion 3 ately. to the ambient. noise; meansforrendering;

said. pickeuprinoperativerduring the-operationof said; setting-= means,; and -meansto render, said pickeup/operativeaaiter the volume setting means: hasz functioned, saidlastthreemeans being con-- trolled by-a -re :ord.ohang er-.- M HARRY OLSON. J OHN PRESTON.

REFERENCESCITED The-follo.wingcreferences are? of record" in the; file of. this: patent?- ammo STATESLPATENTS Number Name. Date 2,338,551 Stanko- Jan. 4, 1944 2,382,848 Baumgartner Aug. 14, 1945 2,392,218 Anderson-mama .Jan. 1,-1946' 

